Brachytherapy is a known medical treatment for tumors and the like. More specifically, brachytherapy is a radiation treatment which entails the use of a solid or enclosed radioisotopic source positioned either on the surface of the body of the patient or at a short distance from the area to be treated. One form of brachytherapy is sometimes referred to as "interstitial" brachytherapy, in which radioactive implants are inserted into a tumor to be treated. Radioactivity from the implant shrinks the tumor or preferentially kills the cancerous cells making up the tumor, resulting in successful treatment of the patient. The present disclosure will use the word "brachytherapy" to refer to this latter form of treatment.
Brachytherapy typically involves the steps of positioning the end of a needle, cannula, catheter, or other elongate member or the like in or near the tumor; inserting a radioactive material into the needle, cannula, catheter or the like; allowing the radioactive material to remain near the tumor for a specific length of time; and removing the radioactive material and the needle, cannula, catheter, or other elongate member or the like after the treatment time has expired. In general, the order of the positioning and inserting steps is chosen as desired, depending upon the particular tumor being treated, the nature of the radioactive material and the characteristics of the needle, cannula, catheter, or elongate member or the like being used. Of course, access to the tumor can be established prior to the positioning and inserting steps via an introducer sheath or another needle, cannula, catheter or the like.
The radioactive material introduced during brachytherapy is often contained in a plurality of pellets or "seeds" which are inserted into an open end of the needle, cannula, catheter, or other elongate member and the like. Such seeds are sealed to prevent the leakage of the radioactive material from them. A stylet or other push rod is often used to advance the seeds to an appropriate position in the elongate member.
One commonly used seed comprises an iridium or iridium/platinum alloy core encased in a sheath of platinum. The iridium is irradiated to render it radioactive, in particular, to yield gamma-emitting .sup.192 Ir. A variety of other radioactive materials are known for this purpose, and are equally useful in brachytherapy. Typically, the radioactive seeds are 3 mm in length; during use, the individual seeds are separated by inert spacers of 7 mm length, so that there exists a known standard distance of one centimeter (1 cm) between the centers of the seeds. Knowledge of this distance is useful to the treating physician or surgeon for a variety of known reasons. The diameter of the radioactive seeds is selected as desired for the tumor to be treated, typically at or below about 0.040 in. (1.0 mm) diameter.
A number of practical problems have been encountered with existing apparatus for performing brachytherapy procedures. For example, it is often difficult to insert the radioactive seeds into the small diameter of the needle, cannula, catheter or the like. While it is known to orient such elongate members vertically as an aid to inserting the radioactive seeds, problems are still encountered due to the relatively small diameters employed, and due to the closeness of the diameters of the seeds (and spacers) and the interior diameters of the elongate members.
Moreover, the plastic materials often employed as handles for the elongate members are susceptible to generating an appreciable amount of static electricity. Such static electricity can cause the synthetic materials conventionally employed as spacers to cling to the handle ("static cling"), making it impossible to load the spacers into the elongate member through the handle. Such static electricity, when discharged, can also generate interference with some of the various sensing and other equipment present in the operating room. Finally, and perhaps most importantly, a static spark can be an ignition source in the presence of the oxygen and/or ether commonly employed within the operating room.
Another drawback to some brachytherapy devices (in particular, in those devices in which the elongate member is rigid) is the relative lack of control over the stylet or other push rod used to advance and position the radioactive seeds and the spacers. It is highly desirable that the stylet move with a minimal amount of force, since the radioactive seeds are often retained in the elongate member merely by a small (1 mm) wax plug in the distal end of the elongate member. Unfortunately, it has in fact been a common problem that the stylet is so loose within the rigid elongate member that the stylet readily falls outside the operating field, e.g., to the floor, if not carefully grasped. Since such a mishap can occur while the radioactive seeds are being inserted into the elongate member, too loose a stylet can increase patient and physician exposure to the seeds by what can be an appreciable amount. Too tight a fit between the stylet and elongate member is undesirable, however, because of the fine tactile feedback needed to sense when the seeds are completely inserted in the elongate member and abutted against the wax plug. A force sufficient to overcome undue friction can also unintentionally cause the stylet to eject the wax plug and radioactive seeds when such friction is overcome.
It would be highly advantageous to have a brachytherapy device which included a handle for the elongate member that facilitated the introduction of the radioactive seeds and the spacers into the elongate member. It would also be highly advantageous to have a brachytherapy device which included a handle that was anti-static or static electricity-free, or that was at least static electricity reduced by an amount to substantially eliminate (that is, eliminate to an extent desired for practical purposes) static interference, static cling and the risk of generating an ignition spark. Finally, it would further be highly advantageous to provide a controlled amount of friction between the elongate member and the stylet of a brachytherapy device, such that the stylet would not fall from the elongate member under weight of the stylet, yet also such that only a minimal amount of force was needed to overcome that friction, and such that such friction could be provided virtually the entire time any portion of the stylet was received in the elongate member.